James Nesbitt on playing a neurosurgeon and his role in the new Hobbit film

Walking through the assorted wards and operating theatres, it’s easy to imagine the place could be used to save lives, instead of just being a backdrop for series two of Monroe.

And James Nesbitt, kitted out in green scrubs, could almost pass as a real surgeon, too – if it wasn’t for the enormous Parka he’s wearing to keep warm.

The actor has taken a few weeks off from filming The Hobbit trilogy to reprise the role of Gabriel Monroe; right now he’s pacing the corridor outside the main operating theatre set, waiting to shoot some final scenes. Immediately, any illusion of reality is shattered.

But to get to this stage, Nesbitt has witnessed the sharp end of what this drama is all about. Learning lines is one thing, but knowing first hand the difference between a parietal lobe and an earlobe is another, and Nesbitt oversaw several operations to give him a rare glimpse of the role.

“That was absolutely key, right at the beginning,” he says. “For a start because I didn’t know what to expect. I wasn’t squeamish and I think subconsciously that helped me a great deal to play the character. I saw the brain and all its gore, I saw the violence of getting into the brain.

“It’s very industrial getting in there – the drilling, the sawing – but then I’ve also seen the incredible delicacy with which the surgeons work and the importance of their good hands, their love and fascination with the brain, their courage and knowing that what they do may wreck someone. So, yeah, that’s been vital.”

During the show’s 2011 run, the brilliant neurosurgeon divided his time between operating on brain tumours and coping with his failed marriage to estranged wife Anna.

Series two picks up 18 months later, and life has changed for many of those employed at St Matthew’s: Monroe has moved into his new bachelor pad, colleagues Shepherd and Bremner are parents to baby Louis, and there is a new head of clinical services in town, Alistair Gillespie (played by Neil Pearson) to make life difficult for Bremner and our eponymous hero.

Tracy-Ann Oberman also joins the cast as Lizzie Clapham, a nurse specialist who offers emotional support for neuro and cardiac patients. Naturally, there’s no shortage of drama in episode one, as Monroe and Gillespie are forced to operate together following a road traffic accident.

During a break between takes, Nesbitt explains to me that the first series laid much of the groundwork for this one. “The first series was a success because the characters were all different, but they were brought together,” he says. “I think it was important to have the young actors and see how they develop. That will work to our favour in series two.”

Nesbitt is also just getting used to the medical jargon he needs to reel off to pass as the real deal. “It becomes part of the language in the same way that if you’re playing any kind of role,” he says. “You steep yourself in the appropriate background. I’ve loved it because it’s something I never knew anything about really. And I’ve got the odd bit of medical literature at home which I can tap into if I’m learning lines for the next day.”

It is no hardship that the scripts are penned by his old friend, Pete Bowker, who wrote the series with Nesbitt in mind. “He certainly knows how to write for me,” Nesbitt agrees, nodding. “He makes my job much easier, and it means he can ask me more challenging questions because he has the voice, so it’s a joy to say Pete’s words.

“In episode one there is what will hopefully be a very funny dinner party scene, because the dynamic with my wife has changed now. She’s left me and my son has some rather shattering news. I loved doing that scene because it was also quite an opportunity to let go a bit. The characters had had a few drinks, and having seen it, I loved that.”

Monroe is just one of a string of acclaimed roles. The actor acknowledges many of them as his favourites: Bloody Sunday, the TV movie in which he played Irish campaigner Ivan Cooper, is the first on his list. “It’s been well-documented,” he says, “but I said that it was important for me not just as an actor, but as a person, trying to understand where he came from, and also the impact that art could have on the immediate history of where I came from.”

Cold Feet, the popular series in which he played the lead opposite Helen Baxendale, gets a mention, too. “Clearly Cold Feet had a major impact in terms of bringing me to a wider public,” he says. But he also has a place in his heart for the 1991 film, Hear My Song, about Irish tenor Josef Locke, in which he played talent agent Fintan O’Donnell, a pal of Liverpool nightclub owner Mickey O’Neill (played by Adrian Dunbar). It was a breakthrough role that won him critical acclaim, although it was to be a few more years before he really hit the big time with Cold Feet. “I look back so fondly on it,” he adds, “I often can’t remember what I did yesterday, but I remember what I did during that film.”

Nesbitt acknowledges that all of his jobs have been important in some way or other, though. “Michael Winterbottom, whom I used to do a lot of films with, would say, ‘Your next job is your first job’, and that’s been the case.”

There’s a lot in the pipeline, too, with Monroe about to air and The Hobbit: An Unexpected Journey released at Christmas. Nesbitt isn’t supposed to be talking about Peter Jackson’s Lord of the Rings prequels, though. “Yeah, it’s been exciting,” he says, wary about revealing too much. A great epic year in a wonderful epic country.” But is he aware of the attention his role as the dwarf Bofur – one of the 12 companions of Thorin and Bilbo on the Quest of Erebor – is going to generate, given the fan community’s thirst for all things Hobbit? “Well it’s something that I didn’t really know about, but they’re slowly letting us know about just how fascinated and obsessed people are with it all over the world,” he says, smiling.

Although we know that two more Middle Earth adventures will be released (Jackson has announced a total of three films within three years), it remains to be seen whether Nesbitt will be back for more Monroe after this run. But there’s no chance of him losing enthusiasm soon.

“The minute I get jaded is the minute someone should push me off the acting cliff,” he says, laughing, before shedding the parka and heading back on  set.

• Monroe starts on  STV on Monday